The present invention relates to a device for separate application of a gluing system comprising at least two components, such as a resin component and a hardener component, onto a substrate, and an application method wherein said device is used.
Separate application of the components of a gluing system, such as resin and hardener components, is known in the art of gluing and offers the advantages of providing the components applied onto the substrate in a not thoroughly mixed condition. The actual mixing of the components applied is obtained in the further processing of the substrate, such as the pressing of two or more such substrates together, allowing for a longer period of time to lapse between application and pressing, without an undesired extent of curing occurring during said period. Also, since the components are separated in the application device the pot life of the gluing system will be markedly extended, and the risk of clogging will be brought to a minimum.
Sequential application in the form of strands of resin and hardener components by means of an application device comprising two independently mounted tubes, cf. SE-373 525, having a row of orifices through which the resin and hardener components are separately spread after each other onto the substrate, has been used in the prior art in the case of application of phenolic resorcinol gluing systems. This type of application results in more or less random distribution of the strands of one component in relation to the strands of the other component onto the substrate.
Another method of applying resin and hardener components is a special type of curtain application, for example, as that described in EP 286 939 B1. However, in this method a large surface area of the components are exposed to the surrounding atmosphere, leading to increased evaporation of the water contained in the components of the gluing system. Accordingly, this incurs a reduced period of time from the application of the components to application of pressure for pressing, which is a disadvantage when gluing large wooden beams, for instance.
Further, in the case of curtain application, it is hard to prevent the applied components from dripping off from the lamella when the lamella is turned 90 degrees (after the application, which is often necessary since the pressing equipment is often constructed such that the pressure is applied horizontally, i.e., the glue joints will be vertical. Thus, this method of application is more sensitive to variations in viscosity than the strand application method.
However, technical solutions are still sought for the need to find application systems for separate application of the components of a gluing system, which can be adjusted to the gluing system in question and the desired assembly times. By assembly time it is meant the time that lapse from the moment of application of a gluing system onto a substrate to the moment of pressing the substrates to be glued together.
The present invention accordingly provides a device, and a method using the device, by which the above-mentioned problems are overcome.
The device according to the invention is defined in the appended claims. It comprises a unit of at least two hollow members, at least one member for each component, provided with a number of orifices, from which orifices in each member designed to apply the respective component onto a substrate below the hollow members to form strands, the hollow members being positioned above the plane of application, wherein the unit comprises means for adjusting the position of the orifices in at least one of the hollow members in relation to the position of the orifices in the other hollow member(s).
The means for adjusting the position of the orifices, in at least one of the hollow members, in relation to the position of the orifices in the other hollow member(s), can be a common exchangeable nozzle plate covering at least two hollow members or alternatively it can comprise means for moving the hollow members in relation to each other in the cross machine section.
The orifices in the common nozzle plate can be arranged so that the later applied strands of one component substantially overlap, do not overlap, or do not contact, respectively, the corresponding strands of the previously applied component(s).
A common nozzle plate it may be suitable when the centre to centre distances between the hollow members is from about 5 mm to 900 mm, provided that the total distance, centre to centre, between the two most distant hollow members is no more than about 900 mm.
The moving means can move the hollow members in relation to each other in the cross machine direction. In this way the position of the orifices in at least one of the hollow members can be adjusted in relation to the position of the orifices in the other hollow member(s). Thus, the position of the hollow members in relation to each other can be adjusted so that the later applied strands of one component substantially overlap, do not overlap, or do not contact, respectively, the corresponding strands of the previously applied component(s).
With the device according to the present invention the strands can be applied safely and carefully at the accurate position on the substrate.
The device can be provided with guiding means, which are connected to the application unit, in order to prevent the components from falling onto the edges of the substrate that are not to be glued. The guiding means, during application, engage with the contour of the substrate in the machine direction, while the unit is being held movable in the cross machine direction.
The method according to the invention is defined in the appended claims. It comprises use of the above-described device for applying a gluing system of at least two components, such as a resin component and a hardener component, in the form of strands, onto a substrate.
The substrate is suitable fed under the hollow members through the device.
Depending on the reactivity of the components in the gluing system and the desired assembly times, the later applied strands may overlap, do not overlap, or do not contact, respectively, the corresponding previously applied strands of the other components.
As used here, the term xe2x80x9cstrandxe2x80x9d also comprehends the meaning of the term xe2x80x9cribbonxe2x80x9d, also conventionally used in the art, and any other like term